Internet Protocol Television (IPTV) is an emerging technique for delivering broadcasted TV services over an IP network, which is typically configured as a broadband access network. Currently the predominant IPTV service is Broadcast TV, where normal non-IPTV channels, as well as additional channels with low penetration can be transmitted over a broadband network from a super head-end to the end-user's STB (set top box).
MPEG (Moving Picture Experts Group) transport streams are commonly used for the purpose of transporting video, audio and text packets in IPTV networks, as well as in terrestrial, satellite and cable TV networks.
An MPEG stream is typically containing several elements, which are all needed for providing an ultimate user experience. If one UDP (User Datagram Protocol) packet is dropped, several of these smaller packets are lost, which may result in that the user experience is affected in a negative way. One way of solving this problem is to keep track of all sent packets on both the server and the client side. If a packet is lost, the client will request a re-transmission of the lost packet.
Several solutions for handling re-transmissions have been suggested, all having in common that the network packets have to be modified by adding an additional RTP (Real-Time Transport Protocol) header. The added RTP header does, however create problems for all STB's that does not support any RET (Re-transmission) mechanism. In order to overcome this problem, a client has to be modified such that the added RTP header can be understood by the client, even if the re-transmission feature is not even supported by the client.